Polish pasport - entry to the UK

Poland, like the UK, is part of the European Union which allows freedom of movement within the EU borders to all its citizens. Whether a Polish passport holder resident outside the EU is entitled to the same freedoms is the question you need to ask of the Polish/UK consulates in the US. Ordinarily a one way ticket would be a red flag to an immigration officer.

The countries have to be in so called Schengen zone to allow free movement. Poland is in S.Z. UK is not. It's up to immigration officer to decide if he will be satisfied with one way ticket. Probably if you show him US green card, he will be.

Schengen is about border controls and is separate from the EU Treaty which allows any EU citizen (passport holder?) to enter, without the need for a visa, and move around freely in all the countries of the EU. Further and as an example, although the UK is not part of Schengen, we can stay/live (and work) in any EU country for as long as we want without having to seek permission from the individual countries concerned. The two should not be confused.

So, is it a one way or a round trip ticket ? :)

Ido - check with the consulate. The moot point is whether with a Polish passport you are/or can be treated as an EU citizen. We have lots of Polish people working in the UK (including my hairdresser), they can come and go as they please.

I am not qualified and therefore reluctant to give you a yes or no answer. But the UK Borders Agency site seems to say that if you do not require an entry visa to enter the UK there is no requirement to show anything more (eg return ticket, bank statements etc etc) than your passport as proof of identity before being allowed in. http://www.ukba.homeoffice.gov.uk/visas-immigration/do-you-need-a-visa/